JPS6225842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to gas turbine engines, and more particularly to gas turbine engine rotor and shroud assembly apparatus and methods.

The normal assembly of a stationary shroud and associated components around a turbine rotor creates an inherent eccentricity between the center of operation of the rotating member and the surrounding stationary structural member. The main reason for this eccentricity is the unavoidable accumulation of machining tolerances as a result of the combination of various structural components between the bearing and the turbine shroud. Such tolerance accumulation is on the order of 0.005 to 0.015 inches (0.177 to 0.431 cm) for a typical gas turbine engine, and considering that this eccentricity must be accommodated by increasing tolerances, this reduces turbine efficiency. Approximately 0.5~1.5 of
It corresponds to a loss of %.

One method that can reduce eccentricity without requiring increased tolerances is to perform post-assembly machining. For turbo engines where the high-pressure turbine is the main source of eccentricity, this method involves mounting all low-pressure turbine rotors and structural members on a vertical turret lathe and machining the high-pressure turbine shroud as precisely as possible to make it concentric with the bearings. There is a need to. This method is not only difficult and time consuming, but also requires the use of expensive tools and equipment.

Another drawback of machining methods is that concentric or near-concentric arrangements can only be achieved for that particular combination of parts. After the engine undergoes normal deterioration,
As structural members wear or warp, eccentricity tends to reappear and increase over time, thus requiring time-consuming and costly machining to correct it again. Furthermore, if some parts are replaced or replaced during rework of the engine, the resulting eccentricity must again be corrected in this undesirable manner.

Briefly explaining the present invention, a pair of adjacent annular members are selected from among members that constitute a stationary structure between a rotor bearing and a stationary shroud. These 2
Each part is machined as desired,
Its outer and inner surfaces are eccentrically related by a predetermined amount. The two members are then assembled with the remaining stationary members and then rotated to a selected position to reduce eccentricity between the rotor bearing and the shroud. By appropriately selecting the degree of eccentricity caused by machining and the position at which the two members are rotated,
The inherent eccentricity resulting from the accumulation of machining tolerances can be substantially offset.

According to another aspect of the present invention, the eccentricity applied to each of the two members is made equal, and the eccentricity of one of the members is set so as to cancel the eccentricity of the other at the initial stage of engine assembly.
Place parts relative to each other. Measurements are then taken to determine the amount and direction of inherent eccentricity between the rotor bearing and the static shroud. This measurement information can then be used to determine the optimal rotational position of the two members to offset the measured eccentricity.

According to still another aspect of the present invention, position determination is performed primarily using a calculation chart (nomograph) that displays vectors of possible positions of eccentricity and related circumferential arrangement conditions of two members for offsetting these eccentricities. be able to do so. In this way, it is easy to use the measured eccentricity and plot it on a graph to find the best possible position for rotating the two members to obtain a virtually concentric arrangement. .

Next, the present invention will be explained with reference to embodiments shown in the drawings.

FIG. 1 is a longitudinal cross-sectional view of a conventional turbine structure, and the present invention is incorporated therein with the numeral 1.
It is collectively referred to as 0. The turbine structure includes a row of circumferentially spaced high pressure turbine blades 11;
a row of circumferentially spaced low pressure turbine vanes 1;
2 and multiple rows of alternating low pressure blades 13 and vanes 14 to which hot gas from the combustor is supplied to drive the high and low pressure spools in a manner well known in the art. In the case of high pressure turbines, blades 11
are mounted circumferentially spaced about a high pressure turbine disk 16, and a high pressure turbine shaft 17 extending forwardly from the disk 16 is drivingly connected to a compressor (not shown). A high pressure turbine stub shaft 18 extends rearwardly from the high pressure turbine disk 16 to a bearing 19 . The bearing 19 thus supports the high-pressure turbine shaft 17.

The low-pressure turbine blades 13 are mounted on the outer periphery of the low-pressure turbine disks 21, and these disks 2
1 are interconnected by fasteners 20 to collectively form one drum. This drum is drivingly connected to low pressure shaft 22 by an outer low pressure turbine cone shaft 23 and an inner low pressure turbine cone shaft 24.

The bearing 19 is interposed between the radially outer high pressure turbine stub shaft 18 and the radially inner low pressure turbine shaft 22 . An inner race 26 is fixed to the low pressure shaft 22 by a plurality of fasteners 27, and an inner race 26 is fixed to the high pressure turbine stub shaft 18 by a plurality of fasteners 27.
Outer race 28 is secured in a similar manner. In this way, the low pressure shaft 22 supports the high pressure turbine disk 16.

Support for the low pressure shaft 22 is provided by bearings 29. An inner race 31 of the bearing 29 is secured to the outer periphery of the low pressure shaft 22, and an outer race 32 is secured to a stationary bearing cone 33 with a plurality of fasteners 34. On the other hand, the bearing cone 33 is rigidly fixed to the stationary low pressure turbine frame 36 with a plurality of fasteners 37.

Considering the outer flow path of the turbine gases, the low pressure turbine casing 38 is rigidly attached to the low pressure turbine frame 36 and extends forward of the frame. A plurality of support flanges 39 that hold the outer ends of the low-pressure turbine vanes 14 are provided on the radially inner side of the low-pressure turbine casing 38 . A honeycomb shroud 41 is provided between a pair of adjacent support flanges 39 , and a honeycomb shroud 41 is provided between each pair of adjacent support flanges 39 .
are closely surrounded in a manner well known in the art.

At the front end of the low pressure turbine casing 38, a low pressure shroud support 42 and a low pressure nozzle support 4 are provided.
3 and a combustor casing 44 are combined and installed. These three annular members are secured to the outer flange 46 of the low pressure turbine casing 38 with a plurality of circumferentially spaced fasteners 47 . 1 and 2, the low pressure shroud support 42 is provided with an annular groove 48 for receiving and retaining the low pressure turbine shroud. Similarly, the low pressure nozzle support 43 is provided with a lip 49 for receiving the flange of the low pressure nozzle 12 in supporting relationship. Low pressure nozzle support 4
One end of a high pressure shroud support 53 is fixed to the radially outwardly extending flange 51 of No. 3 with a plurality of fasteners 52. As shown, the high pressure shroud support 53 has a pair of annular flanges 54 and 56 that serve to forcefully support and position the high pressure turbine shroud 57 via suspension brackets 58 and 59. fulfill.

It is particularly desirable to position the shroud 57 concentrically with respect to the high pressure turbine blades 11 with minimal clearance required during various periods of operation. The clearance between the rotating blades and the stationary shroud can be adjusted to suit different static and transient operating conditions by various ways of controlling the thermal growth of the high pressure shroud support 53. Assembled high pressure turbine shroud 5
The roundness of 7 can be achieved by simply machining the shroud into a round shape.

However, even if the high pressure turbine shroud 57 is round, problems arise if the shroud 57 is not concentric with the high pressure turbine blade row 11. Accommodating this eccentricity by grinding the high pressure turbine shroud 57 so that it is concentric with the high pressure turbine blade row 11 is a more complex and expensive operation than the machining operations described above. Furthermore, even if this complex operation were performed, subsequent replacement of even one of the stationary components mentioned above would significantly change the position of the high-pressure turbine shroud 57, and the shroud would once again be eccentrically positioned relative to the turbine blades. .

When considering the assembly of new engine parts, even though the various parts are designed and manufactured to dimensions and tolerances that should result in a concentric arrangement in the assembled condition, there is an inherent eccentricity between stationary and rotating parts. Cheap. That is, assuming that the turbine blade row 11 is concentric with the bearing 19, cumulative static component tolerances tend to appear between the bearing 19 and the static shroud 57. The present invention recognizes this inherent eccentricity and provides methods and apparatus for reducing or substantially correcting such inherent eccentricity.

2-5, the low pressure shroud support 42 and the low pressure nozzle support 43 have an annular shape and can be rotated to various positionable circumferential positions depending on the requirements for tightening to the final position. For convenience of explanation, it is assumed that the number of bolt holes 61 passing through both the low pressure shroud support 42 and the low pressure nozzle support 43 is twelve. Further, it is assumed that the low pressure nozzle support 43 can be placed at any of four circumferential positions as required to facilitate insertion of the boroscope. Therefore, the low pressure shroud support 42 can be rotated into 12 different positions relative to the low pressure nozzle support 43, and the low pressure nozzle support 43 can be rotated into 4 different positions relative to the high pressure shroud support 53.
Can be rotated into two different positions. Therefore, the total is 48
A combination of possible positions in the circumferential direction is obtained.

To compensate for the inherent eccentricity of the assembled machine, low pressure shroud support 42 and low pressure nozzle support 43 are formed with relatively eccentric outer and inner surfaces, respectively. 2 and 3, low pressure shroud support 42
has a radially outer annular surface 62 that fits in intimate relation to the low pressure turbine casing 38 and has a radius A from a center point S. The radially inner annular surface 63 of the support 42 is located at a distance Y from the center point S.
It has a radius B from the center point T that is shifted upward by . As a result, the cross-section of the low pressure shroud support 42 is eccentric or offset, as shown exaggerated in FIG.

2 and 4, low pressure nozzle support 43 has an outer surface 64 that telescopes in intimate relation to inner surface 63 of low pressure shroud support 42 and has a radius C from center point T. An inner surface 66 at the other end of the low pressure nozzle support 43 has a radius D from a center point S offset a distance Y downward from the center point T. The eccentric relationship of outer annular surface 64 and inner annular surface 66 is also shown exaggerated in FIG.

FIG. 5 shows the low pressure shroud support 42 and low pressure nozzle support 43 in the assembled position. As can be seen, the upward displacement of the inner surface 63 of the low pressure shroud support 42 is offset by the equal distance Y downward displacement of the inner surface 66 of the low pressure nozzle support 43. When assembled in this position, the center of the shroud does not change as a result, for example with respect to the low pressure turbine casing. Once it has been determined that the stationary structure is substantially free of inherent eccentricity as described above, the two members, low pressure shroud support 42 and low pressure nozzle support 43, can be assembled in this relative position, with high pressure shroud 57 maintained concentrically with respect to the turbine rotor. However, if an inherent eccentricity is found as a result of tolerance accumulation or for some other reason, the two stationary members, namely the low pressure shroud support 42 and the low pressure nozzle support 43, can be arranged as described above. Compensate or correct this eccentricity by relative rotation to either position. In order to facilitate the selection of the most appropriate circumferential position among the 48 possible positions, a calculation chart was created that specifically shows the effect that these different positions have on the movement of the center of the combination.
Such a calculation chart is shown in FIG. Here, the vertical misalignment distance Y is 0.010 inches (0.254
mm). Therefore, the total amount of misalignment is at most 0.020 inch. The amount of eccentricity or distance is plotted on the vertical axis, and the direction or angle of eccentricity is plotted on the horizontal axis. This diagram only shows 12 positions. However, four different horizontal scales are shown, one of which corresponds to one of the four possible positions of the low pressure nozzle support 43. Therefore,
For each of the four possible positions of the low pressure nozzle support, twelve possible positions of the low pressure shroud support are shown. This calculation chart can be used to determine which of the 48 possible positions is optimal for compensating for the actual inherent eccentricity of the assembly device.

The process of correcting the inherent eccentricity of the assembled turbo engine will be briefly described below. First, the module is assembled with the low pressure shroud support 42 and the low pressure nozzle support 43 arranged at offset circumferential positions as shown in FIGS. Next, the magnitude and angular position of eccentricity of the shroud 57 with respect to the bearing 19 are measured. Write these values on a calculation chart to find the rotatable position that reduces eccentricity. Next select the one position that will give the maximum correction and place the low pressure shroud support 4
2 and low pressure nozzle support 43 to the selected position.

Two examples will be given to specifically explain the usage of calculation charts. Assume that measurements have determined a natural eccentricity of 0.012 inch (0.305 mm) in the 100° direction when the low pressure module is in the assembled condition.
To correct for eccentricity, the module must be moved in the opposite direction, so write the values of 0.012 inch and 280° on the graph. Regarding the four horizontal scales, there are two (and) positions in which the low pressure shroud support can be moved to move the assembly toward positions K and L where the eccentricity is completely offset. The next step is to determine which of the 48 possible locations is optimal or closest to these two points. Since the closest direction to 280° is 300°, it is immediately clear that point M is closest to point K or L. Therefore, the optimal choice is to place the low pressure nozzle support 43 in position and the low pressure shroud support 42 in position 10.

Since the actual eccentricity point does not fall exactly within one of the 48 possible positions, moving the two members to this new position does not completely cancel out the actual eccentricity. However, the eccentricity is significantly improved and the eccentricity is almost completely corrected.

Here's another example: Assume that an eccentricity of 0.014 inches (0.356 mm) is measured in the 230° direction. Two possible positions for complete correction are indicated by points P and Q (low pressure shroud support position or). The closest possible positions to these points are points R and S, so move the stationary member to one of these two combinations, i.e. move the low pressure nozzle support to position and the low pressure shroud support to position 3. Alternatively, the eccentricity can be substantially corrected by moving the low pressure nozzle support to position 6 and the low pressure shroud support to position 6.

The use of calculation charts is just one example of many methods for determining the optimal selection of component locations.
For example, a simple computer program could be developed for this purpose, or a table could be created to make the selections.

[Brief explanation of the drawing]

1 is a longitudinal cross-sectional view of a turbine structure constructed in accordance with the present invention; FIG. 2 is an enlarged view of selected portions of the turbine structure; and FIG. 3 is a view taken along line 3--3 of FIG. A cross-sectional view of the shroud support. Figure 4 is a cross-sectional view of the nozzle support taken along the line 4--4 in Figure 2. Figure 5 is a cross-sectional view of the shroud support as seen along the line 5--5 in Figure 1. The sectional view shown and FIG. 6 are calculation charts showing possible positions of the two members in the circumferential direction with respect to eccentricity. 11... High pressure turbine blade, 19... Bearing, 3
6...Frame, 38...Casing, 42...Shroud support, 43...Nozzle support, 44...Combustor casing, 57...High pressure turbine shroud, 62...Outer surface of 42, 63...Inner surface of 42, 64...43 Outer surface, inner surface of 66...43, S...center point of 62, T...center point of 63, A...
radius of 62, B...radius of 63, C...radius of 64,
D...Radius of 66, Y...Eccentric distance.

Claims (1)

[Scope of Claims] 1. In a turbomachinery structure of a type having a rotor supported by bearings and a shroud supported by an enclosing frame, the shroud being likely to be eccentric with respect to the bearing, (a) the centers are radially adjacent to each other; (b) a first frame member having an outer annular surface and an inner annular surface whose centers are offset from each other by a second predetermined distance in the radial direction; two frame members; and (c) means for relatively rotating said first and second frame members to selected positions to substantially reduce eccentricity between said shroud and bearing. 2. The turbomachine structure of claim 1, wherein the first and second predetermined distances are substantially equal. 3. The turbomachine structure of claim 1, wherein said first and second frame members are telescopically interconnected. 4. The turbomachine structure of claim 3, wherein the inner annular surface of the first frame member is substantially co-centered with the outer annular surface of the second frame member. 5. The center of the outer annular surface of the first frame member and the inner annular surface of the second frame member is
4. The turbomachine structure of claim 3, wherein the first frame member is offset in the same direction from the center of the inner annular surface. 6. The turbomachine structure of claim 5, wherein the first and second predetermined distances are substantially equal. 7. The turbomachine structure of claim 1, wherein the first frame member comprises a low pressure shroud support member. 8. The turbomachine structure of claim 1, wherein the second frame member comprises a low pressure nozzle support member. 9. In a turbomachinery structure of a type having a rotor supported by a bearing and a shroud supported by an enclosing frame, where the shroud is likely to be eccentric with respect to the bearing, in reducing the eccentricity, (a) a first frame member; (b) in manufacturing the second frame member, the centers of the outer annular surface and the inner annular surface are offset from each other by a first predetermined distance; (c) assembling the first and second frame members into a stationary structure interconnecting the bearing and shroud; (d) A method for reducing eccentricity in a turbomachinery structure having the steps of: rotating two frame members to selected circumferential positions to substantially reduce eccentricity between said shroud and bearing. 10. The method of claim 9, wherein the first and second predetermined distances are substantially equal. 11. The method of claim 9 in which the first and second frame members are assembled adjacent to each other. 12. The method of claim 9, including the step of measuring eccentricity of the shroud relative to the bearing after assembly. 13 The first and second frame members are
10. The method of claim 9, wherein the radial offset of the frame member is in the opposite direction from the radial offset of the second frame member. 14. The method of claim 12, including the step of determining circumferential positions of the first and second frame members that offset the measured eccentricity. 15. The method of claim 14, including the step of circumferentially rotating the first and second frame members to a position closest to the measured offset position.